1. Field of the Invention
This invention relates to improvements in bulk storage and handling systems and particularly to such systems that utilize a flexible inflatable membrane silo liner which inflates under low pressure to gently roll and push material into the angle of repose.
2. Background Art
Although material handling and storage bins such as silos have been known and widely used almost since the dawn of civilization, there is little art on such bins with flexible membrane fluid-assisted discharge. Such art as is known to Applicant has been cited against commonly owned applications, Ser. No. 257,604 filed Apr. 27, 1981, now U.S. Pat. No. 4,421,250, Ser. No. 307,089 filed Sept. 30, 1981, now U.S. Pat. No. 4,496,646, Ser. No. 357,589, filed Mar. 12, 1982, and Ser. No. 357,592 filed Mar. 12, 1982, now U.S. Pat. No. 4,476,998, as well as PCT International application publication No. WO82/03839.
The most relevant of this background art appears to be U.K. Patent No. 1,144,162 published March 1969 which shows a silo with a single flexible liner inflated from the bottom and having none of the sophisticated details and controls which would be necessary to make such silo a success from an operational standpoint.
In connection with the actual construction and installation of such silos using a flexible membrane discharge of the type disclosed in the above-identified prior applications, a number of vexing problems have surfaced. One of these problems involves the inner wall of the flexible membrane for large bins trapping the bulk of the granular materials in its folds as it is expanded thus preventing complete discharge. This is particularly a problem with large bins and it appeared to be insolvable.
Another problem which exists in such bins concerns the incomplete discharge of the material from the bottom of the bin. For example, even though the bin may hold 10,000 pounds of material and the flexible membrane assists in discharging substantially all of the material, a small amount of material such as 50 pounds or more which might remain in the bottom or on top of the clamping ring adjacent the discharge opening is undesirable. If the flexible membrane is clamped to the discharge opening by a clamping ring it cannot operate to discharge the material on top of the clamping ring, and therefore leaves an undesirable amount of material remaining in the bag.
Additionally, it has been found in connection with the commercial size and scale bins that there is need for maintaining the outer wall of the dual-walled flexible membrane bag adjacent the silo wall. The outerwall of the bag is clamped to the silo wall near its top to hold it up, but there is nothing to cause it to conform to the silo wall at an intermediate position and no readily accessible means for causing it to do so.
Additionally, the prior art does not disclose any effective means for control of not only the discharge cycle and preparation of the silo for refilling, but for the overall cyclical sequence together with safety controls to prevent damage to the expensive membrane in the event of accidental overpressure within the bag.